Beneficiaries Equity of the Parent Company (Textual) (Details) - USD ($)					1 Months Ended	12 Months Ended
	Dec. 31, 2018	Dec. 06, 2018	Apr. 11, 2017	Jan. 10, 2017	Jan. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Jan. 03, 2019
Class of Stock [Line Items]
Dividends, Common Stock	$ 33,600,000
Dividends payable, date to be paid	Jan. 22, 2019
Dividends payable, date of record	Jan. 08, 2019
Preferred shares authorized	20,000,000					20,000,000	20,000,000
Preferred shares outstanding	0					0	0
Preferred share redemption charge						$ 0	$ 3,181,000	$ 0
Repurchased and Retired, Shares						1,729,278	0	0
Share Price						$ 12.64
Repurchased and Retired, Value						$ 21,858,000
Common stock price per unit	$ 0.01					$ 0.01	$ 0.01	$ 0.01
Common Stock, Shares Authorized	400,000,000					400,000,000	400,000,000
Upfront costs							$ 499,000
Common shares issued under offering program								0
Cash proceeds, net of issuance costs						$ 416,000	$ 51,225,000	$ 0
Offering Program [Member]
Class of Stock [Line Items]
Common Stock, Shares Authorized				16,000,000
Upfront costs				$ 200,000
Common shares issued under offering program						23,311	2,858,991	0
Weighted average price per share	$ 18.04					$ 18.04	$ 18.19
Cash proceeds, net of issuance costs						$ 400,000	$ 51,200,000
Common shares remain available for issuance	13,117,698					13,117,698
Subsequent Event [Member]
Class of Stock [Line Items]
Authorized Amount									$ 150,000,000.0
Repurchased and Retired, Shares					1,337,169
Share Price					$ 12.92
Repurchased and Retired, Value					$ 17,300,000
Maximum [Member] | Subsequent Event [Member]
Class of Stock [Line Items]
Authorized Amount									$ 150,000,000
BRANDYWINE OPERATING PARTNERSHIP, L.P.
Class of Stock [Line Items]
Dividends, Common Stock		$ 33,600,000
Dividends payable, date to be paid		Jan. 22, 2019
Dividends payable, date of record		Jan. 08, 2019
Preferred share redemption charge						$ 0	3,181,000	$ 0
Repurchase program, number of common unit retired for each common share repurchased						1
Cash proceeds, net of issuance costs						$ 416,000	$ 51,225,000	$ 0
BRANDYWINE OPERATING PARTNERSHIP, L.P. | Series E Preferred Stock [Member]
Class of Stock [Line Items]
Redemption outstanding shares			4,000,000
Redemption price per share			$ 25.51
Accrued dividends paid in cash			$ 2,000,000.0
Preferred share redemption charge			$ 3,200,000
Dividend Declared [Member]
Class of Stock [Line Items]
Dividends Payable, Amount Per Share	$ 0.19					$ 0.19
Dividend Declared [Member] | BRANDYWINE OPERATING PARTNERSHIP, L.P.
Class of Stock [Line Items]
Dividends Payable, Amount Per Share		$ 0.19
Redeemable Common Limited Partnership Units [Member]
Class of Stock [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share						982,871	1,479,799	1,479,799